These teachings relate generally to wireless communications systems and, more specifically, relate to cellular telecommunications of a type wherein dual-system and dual-mode mobile stations are required, when operating in one system, to make measurements from cells of the other system, such as Global System for Mobile Communications (GSM)/Universal Mobile Telecommunications System (UMTS) compatible mobile stations.
The following abbreviations are herewith defined.
Reference can also be made to 3GPP TR21.905, V4.4.0 (2001-10), Third Generation Partnership Project; Technical Specification Group Services and System Aspects; Vocabulary for 3GPP Specifications (Release 4).
A multi-RAT MS is one having both 2G (GSM) and 3G (UMTS) capabilities, i.e., a 2G-3G multimode MS that can obtain service in either a 2G or a 3G network.
In the GSM dedicated mode, that is during a circuit-switched (CS) connection, a GSM/UMTS multimode MS is required to measure and report the quality of surrounding 3G cells. This is done so that the wireless network is enabled to command, if necessary, the MS to perform a handover to a UMTS cell. The identifications of the 3G cells that the MS is required to monitor and report back to the wireless network are transmitted to the MS in a 3G Neighbor Cell list. In order to improve the overall system performance and reduce latency when handing over to a 3G cell it is important that the MS begin the measurement and reporting of 3G cells as soon as possible after entering the GSM dedicated mode, i.e., the MS preferably has immediate access to the 3G Neighbor Cell list.
When operating in the GSM dedicated mode the MS receives the 3G Neighbor Cell list as part of a MEASUREMENT INFORMATION message. As the amount of information carried in the MEASUREMENT INFORMATION message is substantial, the message contents are transmitted in several shorter message instances. As such, it requires some non-trivial amount of time for the MS to receive the 3G Neighbor Cell list from the MEASUREMENT INFORMATION message and to thereby have access to the 3 G Neighbor Cell list. To overcome this problem, i.e., to enable the MS to start the measurement and reporting of 3G cells immediately after entering the GSM dedicated mode, the 3G Neighbor Cell list that is used for the measurement and reporting of 3G cells in the GSM dedicated mode is also transmitted on a Broadcast Control Channel (BCCH) with a SYSTEM INFORMATION Type 2quater (SI2quater) message. This enables the MS to construct the 3G Neighbor Cell list, when operating in the idle mode, from the contents of SI2quater message, and to use the constructed list for the purpose of immediately beginning the measuring and reporting of 3G cells after entering the GSM dedicated mode.
While the use of the BCCH would at first glance appear to solve the problem of obtaining fast access to the 3G Neighbor Cell list, in actuality a General Packet Radio Service (GPRS) attached MS is not required to monitor the BCCH in the idle mode so long as the cell in which the MS is operating has a Packet Broadcast Control Channel (PBCCH). As a result, a GPRS-capable GSM/UMTS dual-mode MS that is monitoring the PBCCH, as opposed to the BCCH, is not able to construct the 3G Neighbor Cell list from the contents of SI2quater message.
It should be noted that the 3G Neighbor Cell list is also provided on the PBCCH with a PACKET SYSTEM INFORMATION Type 3quater (PSI3quater) message. This is done for the purpose of enabling the MS to measure and report 3G cells when operating in the GPRS packet idle and packet transfer modes. However, according to the current 3GPP technical specifications the MS is not allowed to use the 3G Neighbor Cell list that is constructed from the contents of the PSI3quater message for the measurement and reporting of 3G cells when in the GSM dedicated mode. Instead, the MS is expected to use the list constructed from the SI2quater message found on the BCCH. In fact, the 3G Neighbor Cell list constructed from the contents of PSI3quater message is not compatible with the MS messages used for measurement reporting in the GSM dedicated mode. As a consequence, a GPRS attached, GSM/UMTS dual-mode MS is not able to start the measurement and reporting of 3G cells in the GSM dedicated mode, when in a cell that has a PBCCH, before the 3G Neighbor Cell list is received from the MEASUREMENT INFORMATION message.
It can thus be clearly seen that the current state of the affairs is less than optimum for enabling an efficient and timely measuring and reporting of 3G cells by the dual mode GSM/UMTS MS, as the GPRS attached, GSM/UMTS dual-mode MS is unable to start the measurement and reporting of 3G cells, when operating in the GSM dedicated mode in a cell that has a PBCCH, before the lengthy MEASUREMENT INFORMATION message has been received. As a result, the call setup time is increased for the case of calls that are required to be transferred to UMTS before user data can be transferred (e.g., a video call requiring high bit rates provided only by UMTS).
The foregoing and other problems are overcome, and other advantages are realized, in accordance with the presently preferred embodiments of these teachings.
This invention provides a mechanism and an operating protocol for a GPRS attached, GSM/UMTS dual-mode MS to begin the measurement and reporting of 3G cells immediately after entering the GSM dedicated mode, in a cell that has a PBCCH, by enabling the 3G Neighbor Cell list received on the PBCCH to be also be used as initial information in the GSM dedicated mode, in a manner similar to the way in which the 3G Neighbor Cell list is used that is received from the BCCH.
A General Packet Radio Service GPRS, Global System for Mobile Communications GSM/Universal Mobile Telecommunications System UMTS capable mobile station in accordance with these teachings includes a radio frequency transceiver for communication with a wireless network and a controller responsive to a receipt of information from the wireless network for reporting 3G cells when operating in a GSM dedicated mode on a cell that has a Packet Broadcast Control Channel PBCCH. The controller is enabled to report the 3G cells before the receipt of the 3G Neighbor Cell list from the MEASUREMENT INFORMATION message. The information includes a 3G Neighbor Cell list received in a PACKET SYSTEM INFORMATION Type 3quater message on the PBCCH, and a 3G_BA_IND information element received in the PACKET SYSTEM INFORMATION Type 3quater message. The controller reports the 3G cells using a MEASUREMENT REPORT message that reflects a value of the received 3G_BA_IND information element. The controller may also report the 3G cells using an ENHANCED MEASUREMENT REPORT message that reflects a value of the received 3G_BA_IND information element.
In another embodiment a PSI3_CHANGE_MARK information element is received in the PACKET SYSTEM INFORMATION Type 3quater message, and the LSB of the PSI3_CHANGE_MARK information element is used by the mobile station as the 3G_BA_IND information element.
In general, the controller reports the 3G cells to the wireless network before a number of instances of the MEASUREMENT INFORMATION message are received that are defined by a 3G_WAIT parameter.